Two of my three children are overweight. I feel like a failure as a mum and worry my friends judge me

Am I fat?' My nine-year-old daughter asks me one morning standing in front of my bedroom mirror.

'What? Don't be silly!' I say, flustered. 'Why do you say that?'

'Because one of the girls in year three told me I had a big, fat tummy,' she says.

'What a rude thing to say! There's nothing wrong with you. You're lovely,' I tell her. She shrugs and goes back to peering at her profile in the mirror.

The problem is, while she is lovely, my daughter also has a very 'healthy appetite' and has in fact developed a sizeable tummy over the past year or so. She has always loved her food, but just seems to have piled on the weight in recent months.

I've found this to be puzzling and disturbing in equal measure. We don't mainline junk food at home. I like to think we eat well — the usual stuff: spaghetti bolognese, home-made chicken curry, roast dinners.

I do wonder if I overload her plate on occasion, but when I cut back on portions, or replace potatoes with salad, she says she's still hungry.

And I don't want my daughter to think that going hungry — as so many girls and women do in the pursuit of a smaller tummy — is normal or right.

The truth is, I find her fledgling body image and food concerns a very sensitive subject, which makes it hard to broach the topic of her broadening midriff.

I frame my disapproval of her snacking habit in terms of health.

Oatcakes are a better alternative to bagels; yoghurts are healthier than crisps. But still she eats a lot.

Yet I cannot bring myself to talk directly about cutting back on food intake.

We are so aware nowadays of the epidemic of eating disorders that it feels like any talk of dieting is like playing with fire.

As it is, girls are bombarded from all sides with images of perfect, slender bodies and constantly invited to compare themselves. The last thing they need is a parent questioning their eating habits too. I have a friend whose 12-year-old daughter is currently in the hell of anorexia and I can see how horribly damaging it is.

At the same time, however, I know that there are serious health risks to being overweight in childhood.

Last month, a terrifying study from researchers in Germany said that being 'severely obese' as a child can cut life expectancy in half. This means a four-year-old weighing 3st 8lbs, who doesn't lose the extra pounds and continues into adulthood with the same rate of obesity might expect to live to just 39.

Even being overweight at the age of four — classed as weighing 3st 1lb — cuts life expectancy from 80 to 65. Carrying extra weight as a child puts you on a direct path to conditions such as diabetes and heart disease, while losing it cuts the risk dramatically.

The question is: how do I put my daughter on a diet without also giving her lifelong issues around food?

Unfortunately, she is not the only one of my children with whom I have this dilemma.

My younger boy, who's 12 and has been blessed with his father's metabolism, is thin as a rake. But at 14, my older boy has become quite tubby too. The other week I even had to buy him plus-sized school trousers.

So now two of my three kids are overweight. It is very hard when I see them together not to feel like a failure as a mum.

Can I blame genetics? I have never been particularly thin myself, but I have never been what you would call fat either. I was a size 10 until I had children in my early 30s, but now I'm more of a 12 to 14.

Sure, I've found it harder to keep the weight off now I'm at that mid-life perimenopausal stage, where even daily exercise such as dog walking, Pilates or swimming won't dent the small muffin top that's appeared round my middle. But I don't regard myself as large.

No, the problem with my son is fussiness. I swore I'd never be the mum who made multiple meals at dinner time to cater for everyone's hard-to-please tastes, but that is precisely what I have turned into.

Even now, my 14-year-old still mainly eats 'beige' toddler food. It is that or nothing, and again I don't want him to go hungry —though on occasion I have indeed sent him to bed with no dinner rather than capitulate to demands for fish fingers or chicken nuggets.

I've cajoled and bribed, too, but to no avail, and if I'm very busy with work, I often end up taking the path of least resistance. I do not have the energy to sit with my teenager and make him eat green beans. I don't have the time to slave over an oven making endlessly varied plates of cooked-from-scratch food in the vain hope that one of them might tempt him.

To assuage the guilt, I buy multivitamins and probiotics. But there's no getting away from the fact his relatively poor diet is starting to show.

And I do feel guilty — it's made worse by the fact that none of this would have happened around my mother's table. She cooked everything from raw ingredients. We ate it all and did not snack. No one would have dreamt of demanding their own menu or raiding the larder between meals.

But food — and family — culture has changed. We encourage our children to be more autonomous nowadays; to be more in touch with their feelings. To help themselves when they're hungry.

And so I have started hiding the cereal bars I put in my children's lunch boxes to make sure that they stick to their allocated one a day. This makes me feel ashamed and angry.

It doesn't help that some healthy foods have shot up in price recently.

Weight loss experts tell children to snack on nuts or dried fruit, but a single bag of mixed nuts can easily cost £5 nowadays. You can get 20 packets of crisps for that (I don't — but many do).

I refuse to go low fat or zero sugar when those sorts of foods are even more ultra-processed and chemically enhanced than a full-sugar cereal bar.

Still, I hate the fact that we are apparently becoming a 'fat family'. My still-slim husband says that it's probably just a phase and the children will hopefully shoot upwards soon and lose all the puppy fat. But I confess there are times when the worry keeps me awake at night.

I fear, too, that my friends are judging me. I know I used to roll my eyes in secret at a girlfriend who dished out the snacks with wilful abandon to her then-chubby daughter. How mean and ashamed it makes me feel now.

I have another friend whose son seems to live off absolute rubbish — mostly Peperami and pizza — and is still thin as a beanpole. The metabolism issue seems to be key and, also, total pot luck.

And yet, even as I look anxiously at my son's expanding stomach and my daughter's tighter-than-ever jeans, I know that I can't mention it.

I don't want to add to their list of worries by making an issue of their weight.

After many hours of angst, I have come to the conclusion that all I can do is sit tight, try to sneak a few more vegetables in where I can and offer them healthier snacks when they are hungry.

Most importantly, I have to try and lead the way by setting a good example. And that means never mentioning the 'D' word (for diet) in this house.

I only hope next time someone has the insensitivity to comment on my daughter's weight, it will be to compliment her on it. The thought of her looking in the mirror and feeling ashamed of her body breaks my heart.